package com.hmdp.service.impl;

import cn.hutool.core.bean.BeanUtil;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.dto.Result;
import com.hmdp.entity.VoucherOrder;
import com.hmdp.mapper.VoucherOrderMapper;
import com.hmdp.service.ISeckillVoucherService;
import com.hmdp.service.IVoucherOrderService;
import com.hmdp.utils.RedisWorker;
import com.hmdp.utils.UserHolder;
import lombok.extern.slf4j.Slf4j;
import org.redisson.api.RLock;
import org.redisson.api.RedissonClient;
import org.springframework.aop.framework.AopContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.data.redis.connection.stream.*;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.core.script.DefaultRedisScript;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.PostConstruct;
import javax.annotation.Resource;
import java.time.Duration;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;


@Service
@Slf4j
public class VoucherOrderServiceImpl extends ServiceImpl<VoucherOrderMapper, VoucherOrder> implements IVoucherOrderService {

    @Resource
    private ISeckillVoucherService seckillVoucherService;

    @Resource
    private RedisWorker redisWorker;

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private RedissonClient redissonClient;

    private static final DefaultRedisScript<Long> SECKILL_SCRIPT;
    private IVoucherOrderService proxy;

    static {
        SECKILL_SCRIPT = new DefaultRedisScript<>();
        SECKILL_SCRIPT.setLocation(new ClassPathResource("seckill.lua"));
        SECKILL_SCRIPT.setResultType(Long.class);
    }

    private static final ExecutorService SECKILL_ORDER_EXECUTOR = Executors.newSingleThreadExecutor();

    //类初始化之后执行
    @PostConstruct
    private void init() {
        SECKILL_ORDER_EXECUTOR.submit(new VoucherOrderHandler());
    }

    private class VoucherOrderHandler implements Runnable {
        String queueName = "stream.orders";

        @Override
        public void run() {
            while (true) {
                try {
                    //获取消息队列中的订单信息 XREADGROUP GROUP g1 c1 COUNT 1 BLOCK 2000 STREAMS streams.order >
                    List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
                            Consumer.from("g1", "c1"),
                            StreamReadOptions.empty().count(1).block(Duration.ofSeconds(2)),
                            StreamOffset.create(queueName, ReadOffset.lastConsumed())
                    );
                    //判断消息获取是否成功
                    if (list == null || list.isEmpty()) {
                        //如果获取失败，说明没有消息，继续下一次循环
                        continue;
                    }
                    //解析消息中的订单信息
                    MapRecord<String, Object, Object> record = list.get(0);
                    Map<Object, Object> values = record.getValue();
                    VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
                    //如果获取成功，可以下单
                    handleVoucherOrder(voucherOrder);
                    //ACK确认
                    stringRedisTemplate.opsForStream().acknowledge(queueName, "g1", record.getId());
                } catch (Exception e) {
                    log.error("处理订单异常：", e);
                    handlePendingList();
                }
            }
        }

        private void handlePendingList() {
            while (true) {
                try {
                    //获取pending-list中的订单信息 XREADGROUP GROUP g1 c1 COUNT 1 STREAMS streams.order 0
                    List<MapRecord<String, Object, Object>> list = stringRedisTemplate.opsForStream().read(
                            Consumer.from("g1", "c1"),
                            StreamReadOptions.empty().count(1),
                            StreamOffset.create(queueName, ReadOffset.from("0"))
                    );
                    //判断消息获取是否成功
                    if (list == null || list.isEmpty()) {
                        //如果获取失败，说明pending-list没有异常消息，结束循环
                        break;
                    }
                    //解析消息中的订单信息
                    MapRecord<String, Object, Object> record = list.get(0);
                    Map<Object, Object> values = record.getValue();
                    VoucherOrder voucherOrder = BeanUtil.fillBeanWithMap(values, new VoucherOrder(), true);
                    //如果获取成功，可以下单
                    handleVoucherOrder(voucherOrder);
                    //ACK确认
                    stringRedisTemplate.opsForStream().acknowledge(queueName, "g1", record.getId());
                } catch (Exception e) {
                    log.error("处理pending-list异常：", e);
                    try {
                        Thread.sleep(20);
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();
                    }
                }
            }
        }
    }

    //阻塞队列
    //当一个线程尝试从队列里获取元素时，如果没有元素，线程就会被阻塞
    //直到队列中有元素才会被唤醒，并且获取元素
    /*private final BlockingQueue<VoucherOrder> orderTasks = new ArrayBlockingQueue<>(1024 * 1024);
    private class VoucherOrderHandler implements Runnable {

        @Override
        public void run() {
            while (true) {
                try {
                    //获取队列中的订单信息
                    VoucherOrder voucherOrder = orderTasks.take();
                    //创建订单
                    handleVoucherOrder(voucherOrder);
                } catch (Exception e) {
                    log.error("处理订单异常：", e);
                }
            }
        }
    }*/

    private void handleVoucherOrder(VoucherOrder voucherOrder) {
        // TODO 当前是从线程池中获取的一个子线程，不在主(父)线程中了，所以不能从ThreadLocal中拿userId
        Long userId = voucherOrder.getUserId();
        //创建锁对象
        //SimpleRedisLock simpleRedisLock = new SimpleRedisLock("order:" + userId, stringRedisTemplate);
        RLock lock = redissonClient.getLock("lock:order:" + userId);
        //判断是否获取成功
        //获取锁，默认锁不重试等待，锁过期时间为30秒
        if (!lock.tryLock()) {
            //获取失败，返回错误或重试
            log.error("不允许重复下单");
        }
        try {
            //获取代理对象(事务)
            // TODO 这里同样使用AOP上下文是拿不到代理对象的，因为底层也是由ThreadLocal实现的
            proxy.createVoucherOrder(voucherOrder);
            //最后的return方法调用实际上是在当前Impl实现类中调用的
            //但下面的方法加了@Transactional注解，底层会采用动态代理的方式生成当前Impl实现类的代理对象
            //要在Impl实现类的代理对象中调用createVoucherOrder方法，事务才会生效
            //所以直接按照下面的return写法会导致事务失效
            //return this.createVoucherOrder(voucherId);
        } finally {
            //释放锁
            lock.unlock();
        }
    }

    @Override
    public Result seckillVoucher(Long voucherId) {
        //获取用户id和订单id
        Long userId = UserHolder.getUser().getId();
        //获取订单id
        long orderId = redisWorker.nextId("order");
        //执行lua脚本
        Long result = stringRedisTemplate.execute(
                SECKILL_SCRIPT,
                Collections.emptyList(),
                voucherId.toString(), userId.toString(), String.valueOf(orderId)
        );
        int r = result.intValue();
        //判断返回结果是否为0
        if (r != 0) {
            if (r == 3) {
                return Result.fail("该秒杀券不存在");
            }
            if (r == 2) {
                return Result.fail("不能重复下单");
            }
            if (r == 1) {
                return Result.fail("库存不足");
            }
        }
        //获取代理对象
        proxy = (IVoucherOrderService) AopContext.currentProxy();
        //返回订单id
        return Result.ok(orderId);
    }

    /*@Override
    public Result seckillVoucher(Long voucherId) {
        //查询优惠券信息
        SeckillVoucher seckillVoucher = seckillVoucherService.getById(voucherId);
        //判断秒杀是否开始
        if (seckillVoucher.getBeginTime().isAfter(LocalDateTime.now())) {
            return Result.fail("秒杀尚未开始");
        }
        //判断秒杀是否结束
        if (seckillVoucher.getEndTime().isBefore(LocalDateTime.now())) {
            return Result.fail("秒杀已结束");
        }
        //判断库存是否充足
        if (seckillVoucher.getStock() < 1) {
            return Result.fail("库存不足");
        }
        //如果在方法里添加锁，最后锁释放后，其他线程可能会进来执行，此时事务还未提交，也会引发线程安全问题
        //所以要在方法外面添加锁
        Long userId = UserHolder.getUser().getId();
        //创建锁对象
        //SimpleRedisLock simpleRedisLock = new SimpleRedisLock("order:" + userId, stringRedisTemplate);
        RLock lock = redissonClient.getLock("lock:order:" + userId);
        //判断是否获取成功
        //获取锁，默认锁不重试等待，锁过期时间为30秒
        if (!lock.tryLock()) {
            //获取失败，返回错误或重试
            return Result.fail("不允许重复下单");
        }
        try {
            //获取代理对象(事务)
            IVoucherOrderService proxy = (IVoucherOrderService) AopContext.currentProxy();
            return proxy.createVoucherOrder(voucherId);
            //最后的return方法调用实际上是在当前Impl实现类中调用的
            //但下面的方法加了@Transactional注解，底层会采用动态代理的方式生成当前Impl实现类的代理对象
            //要在Impl实现类的代理对象中调用createVoucherOrder方法，事务才会生效
            //所以直接按照下面的return写法会导致事务失效
            //return this.createVoucherOrder(voucherId);
        } finally {
            //释放锁
            lock.unlock();
        }
    }*/

    @Override
    @Transactional
    public void createVoucherOrder(VoucherOrder voucherOrder) {
        //一人一单
        // TODO 当前是从线程池中获取的一个子线程，不在主(父)线程中了，所以不能从ThreadLocal中拿userId
        Long userId = voucherOrder.getUserId();
        //查询订单
        int count = query().eq("user_id", userId).eq("voucher_id", voucherOrder.getVoucherId()).count();
        //是否存在
        if (count > 0) {
            log.error("用户已经购买过一次");
            return;
        }
        //扣减库存
        boolean success = seckillVoucherService.update()
                .setSql("stock = stock - 1")
                .eq("voucher_id", voucherOrder.getVoucherId())
                .gt("stock", 0).update();
        if (!success) {
            log.error("库存不足");
            return;
        }
        //创建订单，返回id
        this.save(voucherOrder);
    }
}